feat(mcp-apps): add Permission Policy support for sandbox iframes by aharvard · Pull Request #6947 · block/goose

aharvard · 2026-02-04T14:48:39Z

Summary

MCP Apps run in sandboxed iframes for security. Some apps need access to browser capabilities like the camera, microphone, or geolocation—for example, a voice recording app or a location-based search.

This PR implements support for UIResourceMeta.permissions, allowing MCP App servers to declare which browser capabilities their UI needs. The host (Goose) reads these permissions and sets the appropriate allow attribute on the sandbox iframe, enabling the Permissions Policy for those features.

Per the spec, hosts MAY honor these permissions, and apps SHOULD NOT assume they're granted—they should use JS feature detection as a fallback.

Supported Permissions

Permission	Iframe `allow` attribute
`camera`	`camera`
`microphone`	`microphone`
`geolocation`	`geolocation`
`clipboardWrite`	`clipboard-write`

Changes

Backend (Rust)

Added PermissionsMetadata struct with optional boolean fields for each permission
Updated UiMetadata to include the new permissions field

Frontend (TypeScript)

Pass permissions from resource metadata through the sandbox bridge
Updated mcp_app_proxy.html to build the iframe allow attribute from requested permissions

Example

An MCP App server can declare permissions in its resource metadata:

{
  "_meta": {
    "ui": {
      "permissions": {
        "camera": true,
        "microphone": true
      }
    }
  }
}

Goose will then render the iframe with:

<iframe allow="camera; microphone" ...>

References

Implements _meta.ui.permissions support per MCP Apps spec Section 2. This allows MCP Apps to request browser capabilities like camera, microphone, geolocation, and clipboard-write access. Changes: - Add PermissionsMetadata struct in goose_apps/resource.rs - Pass permissions through sandbox bridge to proxy iframe - Build iframe 'allow' attribute from requested permissions - Update OpenAPI schema and generated TypeScript types This completes Section 2 (UI Resource Format) of the MCP Apps compliance checklist.

aharvard · 2026-02-04T14:53:24Z

There are a lot of formatting changes across the generated files. Not sure what's going on there.

DOsinga · 2026-02-04T14:59:33Z

crates/goose/src/goose_apps/resource.rs

    pub csp: Option<CspMetadata>,
+    /// Sandbox permissions requested by the UI
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub permissions: Option<PermissionsMetadata>,


can we make this not Option<> and just provide a default implementation? same as for the booleans above. if we just make them non option booelan and initialize them as false, the generated code becomes cleaner and the client easier to read

Copilot

Pull request overview

Adds MCP Apps UIResourceMeta.permissions support so apps can request specific browser capabilities and have Goose propagate them to the sandboxed iframe Permission Policy (allow attribute).

Changes:

Introduces PermissionsMetadata in the Rust API schema and updates UiMetadata to include permissions.
Threads permissions through the desktop renderer/bridge and into the sandbox proxy page.
Regenerates OpenAPI client/types (plus a small behavioral tweak in JSON parsing in the generated client).

Reviewed changes

Copilot reviewed 21 out of 21 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
ui/desktop/src/components/McpApps/useSandboxBridge.ts	Passes `permissions` in the sandbox “resource-ready” notification payload.
ui/desktop/src/components/McpApps/types.ts	Re-exports `PermissionsMetadata` for MCP Apps components.
ui/desktop/src/components/McpApps/McpAppRenderer.tsx	Extracts `_meta.ui.permissions` from resource metadata and passes it into the sandbox bridge.
ui/desktop/src/api/types.gen.ts	Adds `PermissionsMetadata` type and `UiMetadata.permissions` field.
ui/desktop/src/api/index.ts	Re-exports updated generated types (includes `PermissionsMetadata`).
ui/desktop/src/api/core/utils.gen.ts	Generated formatting changes.
ui/desktop/src/api/core/types.gen.ts	Generated formatting changes.
ui/desktop/src/api/core/serverSentEvents.gen.ts	Generated formatting changes.
ui/desktop/src/api/core/queryKeySerializer.gen.ts	Generated formatting changes.
ui/desktop/src/api/core/pathSerializer.gen.ts	Generated formatting changes.
ui/desktop/src/api/core/params.gen.ts	Generated formatting changes.
ui/desktop/src/api/core/bodySerializer.gen.ts	Generated formatting changes.
ui/desktop/src/api/core/auth.gen.ts	Generated formatting changes.
ui/desktop/src/api/client/utils.gen.ts	Generated formatting changes.
ui/desktop/src/api/client/types.gen.ts	Generated formatting changes.
ui/desktop/src/api/client/client.gen.ts	Generated changes; includes empty-JSON-body handling in `parseAs: 'json'`.
ui/desktop/openapi.json	Adds `PermissionsMetadata` schema and wires it into `UiMetadata`.
crates/goose/src/goose_apps/resource.rs	Defines `PermissionsMetadata` and adds `UiMetadata.permissions`.
crates/goose/src/goose_apps/mod.rs	Re-exports `PermissionsMetadata`.
crates/goose-server/src/routes/templates/mcp_app_proxy.html	Builds inner guest iframe `allow` attribute from requested permissions.
crates/goose-server/src/openapi.rs	Registers `PermissionsMetadata` in OpenAPI schema derivations.

Copilot · 2026-02-04T15:00:00Z

crates/goose-server/src/routes/templates/mcp_app_proxy.html

+          if (permissions && permissions.camera) allowList.push('camera');
+          if (permissions && permissions.microphone) allowList.push('microphone');
+          if (permissions && permissions.geolocation) allowList.push('geolocation');
+          if (permissions && permissions.clipboardWrite) allowList.push('clipboard-write');


The permissions checks rely on truthiness (e.g. permissions.camera), so a malformed metadata value like 'true' would unintentionally enable the feature; please validate each permission is exactly true before adding it to the allow list.

Suggested change

if (permissions && permissions.camera) allowList.push('camera');

if (permissions && permissions.microphone) allowList.push('microphone');

if (permissions && permissions.geolocation) allowList.push('geolocation');

if (permissions && permissions.clipboardWrite) allowList.push('clipboard-write');

if (permissions && permissions.camera === true) allowList.push('camera');

if (permissions && permissions.microphone === true) allowList.push('microphone');

if (permissions && permissions.geolocation === true) allowList.push('geolocation');

if (permissions && permissions.clipboardWrite === true) allowList.push('clipboard-write');

Copilot · 2026-02-04T15:00:01Z

ui/desktop/src/components/McpApps/McpAppRenderer.tsx

  const { iframeRef, proxyUrl } = useSandboxBridge({
    resourceHtml: resource.html || '',
    resourceCsp: resource.csp,
+    resourcePermissions: resource.permissions,
    resourceUri,


permissions is passed into the sandbox bridge, but the outer proxy iframe rendered by this component never sets an allow attribute; Permission Policy is intersected across ancestor iframes, so camera/mic/geolocation/clipboard-write will likely stay blocked when the proxy URL is cross-origin (e.g., goosed baseUrl). Consider also setting allow on the React iframe based on resource.permissions.

Copilot · 2026-02-04T15:00:01Z

ui/desktop/src/components/McpApps/McpAppRenderer.tsx

          if (content.text !== cachedHtml) {
            setResource({
              html: content.text,
              csp: meta?.ui?.csp || null,
+              permissions: meta?.ui?.permissions || null,
              prefersBorder: meta?.ui?.prefersBorder ?? true,
            });
          }


Guarding the state update on content.text !== cachedHtml prevents applying updated UI metadata (CSP/permissions/prefersBorder) when cached HTML matches the fetched HTML (e.g. StandaloneAppView keeps cachedHtml set even after session init); update the metadata even when the HTML is unchanged.

Suggested change

if (content.text !== cachedHtml) {

setResource({

html: content.text,

csp: meta?.ui?.csp || null,

permissions: meta?.ui?.permissions || null,

prefersBorder: meta?.ui?.prefersBorder ?? true,

});

}

setResource({

html: content.text,

csp: meta?.ui?.csp || null,

permissions: meta?.ui?.permissions || null,

prefersBorder: meta?.ui?.prefersBorder ?? true,

});

Address PR feedback to simplify generated types by: - Changing PermissionsMetadata fields from Option<bool> to bool with defaults - Changing UiMetadata.permissions from Option<PermissionsMetadata> to PermissionsMetadata - Regenerating OpenAPI types This makes the client code cleaner and easier to read.

…ock#6947) Signed-off-by: Harrison <hcstebbins@gmail.com>

…ock#6947)

aharvard marked this pull request as ready for review February 4, 2026 14:53

Copilot AI review requested due to automatic review settings February 4, 2026 14:53

Copilot started reviewing on behalf of aharvard February 4, 2026 14:53 View session

aharvard requested review from DOsinga, alexhancock, jamadeo and zanesq February 4, 2026 14:53

DOsinga approved these changes Feb 4, 2026

View reviewed changes

Copilot AI reviewed Feb 4, 2026

View reviewed changes

aharvard added this pull request to the merge queue Feb 4, 2026

Merged via the queue into main with commit 2b90c2c Feb 4, 2026
15 of 16 checks passed

aharvard deleted the mcp-apps-permissions branch February 4, 2026 16:57

stebbins pushed a commit to stebbins/goose that referenced this pull request Feb 4, 2026

feat(mcp-apps): add Permission Policy support for sandbox iframes (bl…

7a4ae6a

…ock#6947) Signed-off-by: Harrison <hcstebbins@gmail.com>

kuccello pushed a commit to kuccello/goose that referenced this pull request Feb 7, 2026

feat(mcp-apps): add Permission Policy support for sandbox iframes (bl…

9ca99fa

…ock#6947)

github-actions bot mentioned this pull request Feb 10, 2026

chore(release): release version 1.24.0 (minor) #7102

Open

Tyler-Hardin pushed a commit to Tyler-Hardin/goose that referenced this pull request Feb 11, 2026

feat(mcp-apps): add Permission Policy support for sandbox iframes (bl…

49e0257

…ock#6947)

Tyler-Hardin pushed a commit to Tyler-Hardin/goose that referenced this pull request Feb 11, 2026

feat(mcp-apps): add Permission Policy support for sandbox iframes (bl…

34bc91c

…ock#6947)

BrewTestBot mentioned this pull request Feb 12, 2026

block-goose-cli 1.24.0 Homebrew/homebrew-core#267289

Merged

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

feat(mcp-apps): add Permission Policy support for sandbox iframes#6947

feat(mcp-apps): add Permission Policy support for sandbox iframes#6947
aharvard merged 2 commits intomainfrom
mcp-apps-permissions

aharvard commented Feb 4, 2026

Uh oh!

aharvard commented Feb 4, 2026

Uh oh!

DOsinga Feb 4, 2026

Uh oh!

Copilot AI left a comment

Uh oh!

Copilot AI Feb 4, 2026

Uh oh!

Copilot AI Feb 4, 2026

Uh oh!

Copilot AI Feb 4, 2026

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

Conversation

aharvard commented Feb 4, 2026

Summary

Supported Permissions

Changes

Example

References

Uh oh!

aharvard commented Feb 4, 2026

Uh oh!

DOsinga Feb 4, 2026

Choose a reason for hiding this comment

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Reviewed changes

Uh oh!

Copilot AI Feb 4, 2026

Choose a reason for hiding this comment

Uh oh!

Copilot AI Feb 4, 2026

Choose a reason for hiding this comment

Uh oh!

Copilot AI Feb 4, 2026

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants